3D-printed human-centered design of fNIRS optode for the portable neuroimaging

Functional Near-infrared Spectroscopy (fNIRS) is an optical brain imaging technology based on mapping blood oxygenation levels on the cortical surface of the brain. fNIRS has the potential to become a point-of-care brain monitoring system for localized brain measurements in various medical conditions including brain injury and concussion. Although fNIRS electronic circuit has been miniaturized significantly, one of the least elucidated elements of the portable fNIRS systems is the process for developing optodes (light sources and detectors) for the improvements in skin-optode coupling, signal-To-noise ratio (SNR), user\u27s comfort-level and motion artifact reduction. We have used modern design tools such as 3D printing and laser cutting to fabricate human-centered fNIRS optodes. Feedback was taken from participants of different groups throughout the iterative design process of data collection. Two types of fNIRS optodes were designed; one was based on forehead patch and the other was integrable into an electrode head cap. The optodes were connected to our developed portable fNIRS hardware. The noise characteristics of the optodes for the long-Term brain imaging settings, while subjects were performing physical activities, was systemically studied in each of the iterations and designs. The final front-end hardware design was tested on eight subjects with varying head size, shape and skin tone. Experimental results of SNR and resistance to the motion artifacts show that 3D printing can be effective for the development of fNIRS optode. These fNIRS optodes prove to not only be easy to use and comfortable but also capable of acquiring the fNIRS signal with other brain monitoring modalities such as electroencephalography (EEG)